(57) A combination changing method is used in an access control system which includes
one or more keys encoded at a central console with a function information code, a
key identification information code, an operation select information code and a two-field
key combination information code and one or more locks having at least one memory
level in which a lock identification information code and a lock combination information
code are stored. A key is initially inserted into a selected lock and the data from
the key is transferred to the lock. The lock identification information code is first
compared with the key identification information code If there is no correspondence,
power to the lock is turned off for a set period of time. If the identification information
codes correspond, a test field of the key combination information code is compared
with the lock combination information code. If these correspond, the lock opens. If
the identification information codes correspond but the test field of the key combination
information code and the lock combination information code do not, then the operation
select information code is used to select from a predefined set of operations (logical
andior arithmetic and/or other). The operation selection is then performed on an operand
field of the key combination information code. This results in a computed combination
information code which is compared with the lock combination information code. If
this comparison is successful, the test field of the key combination information code
is stored in the lock in place of the lock combination information code and the lock
opens.
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